An SCTP is a most widely used transmission layer protocol in a communication network at present due to the multi-homing function of the SCTP to a great extent, which allows one SCTP connection to select and switch among a plurality of transmission paths, so that the fault-tolerance capacity of the network is improved.
The so-called multi-homing refers to that data transmission can be performed by one SCTP connection through a plurality of logic links of an Internet protocol (IP) layer among networks. Here, the logic link of the IP layer can also be referred to as a path; and there is a backup relationship between the paths, that is to say, if one path is interrupted, data can be switched to other reachable backup paths for transmission.
In the SCTP, a path fault is not only reflected by physical link interruption or unreachable routing, but also more reflected by worsened link quality, such as packet loss due to congestion, packet loss due to error codes, time delay increase, disorder or the like. In a related art, it is not ideal enough for the SCTP to deal with a link quality worsening situation. For example, path switching is performed only when a certain number of times of continuous message retransmissions is reached according to the requirement of the protocol. Under such condition, upon discontinuous interruption of the network or upon larger packet loss rate, a confirmed message may still be received after several attempts; here the number of attempts may not meet the requirement of the protocol. In this case, even if the network quality of a current path is deteriorated and service transmission is seriously affected, the SCTP may still insist on transmitting data on the original path but not selecting a backup path with better quality, thereby affecting the data transmission speed and quality.
Furthermore, the protocol further specifies that: if the current path is not a preferred path, then when the preferred path is reachable, namely, after a confirmed message or a heartbeat response message is received, the current path will be immediately switched back to the preferred path; here the preferred path is a default path of data transmission. However, the reception of a confirmed message or a heartbeat response message only shows that the network path is reachable, which does not mean the network quality of the preferred path is completely restored. Therefore, even if the preferred path is reachable, a network fault still occurs, data transmission in the case of SCTP coupling is seriously affected, accordingly. Here the SCTP coupling refers to a correspondence relationship between two SCTP ports between which a connection is established, that is to say, a network fault may seriously affect data transmission between two coupled SCTP ports.
It can be seen from the above that the current multi-homing path selection mechanism of the SCTP is designed based on the on and off attributes of a path without taking the impact of network quality of the path on data transmission speed and quality into consideration.